Søren Peder Lauritz Sørensen or S.P.L. Sørensen, was a Danish biochemist who is most known for his introduction of the pH scale in 1909 while studying the effect of ion concentration on proteins.

The pH scale (potential of hydrogen) is a scale that determines the acidic or basic character of an aqueous solution on a range of 0 to 14. The markings below 7 ascertain the acidic character of the solution with those nearing 0 as most acidic. As the number increases from 0-14, basic or alkaline character of the solution increases and acidity gets reduced.

To honor this amazing advancement in science, Google created an interactive game that tests your knowledge of items being either acidic or basic.

Born in 1868 to a farmer in Denmark, Sørensen was originally interested in pursuing a career in medicine instead of chemistry when he started his studies at the University of Copenhagen. However, while studying under the influential chemist, SM Jørgensen, he decided to turn his career ambitions towards chemistry.

While studying for his doctorate, he also acted as assistant in chemistry at the laboratory of the Danish Polytechnic Institute and assisted in a geological survey of Denmark. However, he also managed to find work as a consultant at the royal naval dockyard. He found work in many industries and left his mark in most of them as well!

Sørensen served as the director of the chemical department at the Carlsberg Laboratory in Copenhagen from 1901 to 1938, which is thought to be one the best laboratories in the world. The lab was opened by brewery founder JC Jacobsen in 1875 with the goal of furthering biochemical knowledge in the field of brewing. While working in the lab that was able to discover a better way to isolate yeast, which is now used to brew lager worldwide, he introduced the pH scale.

Sorensen was the head of the prestigious Carlsberg Laboratory in Copenhagen for 37 years, where he worked alongside his second wife, Margrethe Høyrup Sørensen. He retired in 1938 after a period of poor health and passed away the following year.